Re: [libvirt] [PATCH] unlock eventLoop before calling callback function

On Mon, Mar 07, 2011 at 14:13:23 +0100, Jiri Denemark wrote: > On Mon, Mar 07, 2011 at 11:15:38 +0000, Daniel P. Berrange wrote: > > > - if (eventLoop.handles[i].ff) > > > + if (eventLoop.handles[i].ff) { > > > + virMutexUnlock(&eventLoop.lock); > > > (eventLoop.handles[i].ff)(eventLoop.handles[i].opaque); > > > + virMutexLock(&eventLoop.lock); > > > + } > > > > I'm a little concerned as to whether the rest of the code in > > virEventCleanupHandles/CleanupTimeouts is safe, if we release > > the lock here. eg, if some other thread calls virEventAddTimeout > > of AddHandle, is there any way this could cause problems for us > > here. So far I think this is safe because AddTimeout/AddHandle > > will simply append to the end of the array we're iterating over, > > but would like a second opinion before ACK'ing > > I don't think it's safe to unlock eventloop.lock even in the existing > Dispatch{Timeouts,Handles} cases because Add{Timeout,Handle} use realloc which > is allowed to allocate a new array, move the contents of the old one into it > and free the old array. So the for loop can easily end up accessing memory > which has already been freed. Eh, my fingers were faster than my brain :-) Dispatch* are safe since they do anything with the old pointer after getting back from a callback.